The present invention relates to the field of lighting. It finds particular application to surgical lighting systems and will be described with particular reference thereto. It is to be appreciated, however, that the present invention may also find application in conjunction with other types of lighting systems.
Surgical lights used to illuminate surgical sites generally include one or more lamps disposed inside the dome of a dome-shaped reflector which directs light from the lamp to the area to be illuminated. The dome shape of the reflector functions to generally focus the light from the lamps toward the surgical site.
Typically, surgical lights employ a lamp such as a tungsten halogen lamp which is positioned at or near the focal point of the dome-shaped reflector. The light from the lamp is reflected downward by the reflector through an optical lens or diffuser located at an aperture of the light fixture. The diffuser is particularly designed to diffuse the light and to direct and further focus the light in a defined column or cone to an illumination zone.
In order to prevent shadows when the surgeons hand or head passes between the lamp and the patient, the reflector is generally quite large and focuses the light at an illumination zone which is the same size or smaller than the diffuser. The diffuser also functions to diffuse or disperse the light which helps to prevent shadows. The size of the illumination zone in most surgical lights can usually be adjusted by a rotatable sterile handle provided at the center of the face of the light head.
A typical tungsten halogen lamp used in a surgical light includes a tungsten filament that emits energy when electric current passes through the filament. These lamps emit visible light and also emit ultraviolet, infrared, and other undesirable energy. In fact, about 81 percent of the input power to a lamp of this type is converted to infrared energy. Surgical lights are designed to prevent this infrared energy from being directed to the surgical site by the reflector to prevent tissue damage.
The removal or filtering of the infrared energy from the light directed to the surgical site may be accomplished by one or more different devices including heat absorbing glasses, cold mirror coatings, and hot mirror coatings. Hot and cold mirror coatings are called dichroic coatings and transmit energy of certain wavelengths while reflecting energy of different wavelengths. A cold mirror coating permits infrared energy to be transmitted through the coating while the visible energy is reflected. Thus, when a reflector of a surgical light is coated with a cold mirror coating, the coating acts as a filter to remove the unwanted infrared energy from the light which is reflected and directed to the surgical site. The infrared energy passes through the coating and through the glass of the reflector body. The cold mirror coating applied to a glass reflector of a surgical light is quite expensive and may account for over 28 percent of the overall cost of the surgical light.
In addition, the reflectors which are used in many known types of surgical lights are large precision devices formed of glass by compression molding. These glass reflectors are coated with a reflective material and a dichroic coating material. One of the drawbacks of the known surgical lights is that the reflectors due to the expensive glass compression molding process, the cost of the coatings, and the reflector size, are relatively expensive to manufacture.
The present invention contemplates a new and improved technique for overcoming the above-referenced drawbacks and others.